How callback function work?

 

A callback function is a function that is passed as an argument to another function and is called by that function at a later point in time. In other words, a callback function is a function that is called back by another function when a certain condition is met or an event occurs.

Callback functions are commonly used in JavaScript to handle asynchronous tasks, such as reading data from a server or waiting for a user to click a button. For example, if you have a function that makes an asynchronous request to a server to retrieve data, you can provide a callback function as an argument to that function. When the data is available, the original function will call the callback function and pass the data to it.

Here's an example of a simple callback function in JavaScript:

function greet(name, callback) {
  console.log('Hello, ' + name + '!');
  callback();
}

function sayGoodbye() {
  console.log('Goodbye!');
}

greet('John', sayGoodbye);

In this example, the greet function takes two arguments: a name and a callback function. The greet function logs a greeting message to the console and then calls the callback function. The sayGoodbye function is defined separately and passed as the second argument to the greet function. When the greet function is called, it logs the greeting message and then calls the sayGoodbye function, which logs a farewell message to the console.